The field of the disclosure relates generally to a dehumidifier system, and more particularly, to a control system for a reverse flow dehumidifier and methods of dehumidifying an environment.
Desiccant assisted air conditioning systems typically incorporate a rotating desiccant wheel that rotates between two air streams to provide dehumidification or humidification by alternating the energy in a gas phase change process. In such systems, the air delivered to the interior of a space to be conditioned space crosses the desiccant material, which attracts and holds moisture. As the desiccant wheel rotates, the moist desiccant material enters the regeneration air stream where it is heated to release moisture, which is then vented away. Because humidity is a function of vapor pressure, desiccant materials have the ability to remove or add moisture adiabatically; a reversible thermodynamic process in which the energy exchanges result in substantially constant enthalpy equilibrium.
The total desiccant open cycle is somewhat similar to a refrigerant vapor-compression cycle. In a desiccant and air system the heated regeneration air adds energy to the moistened desiccant in a de-sorption process and releases moisture in the regenerating crossing air stream in an adiabatic cooling process. When the desiccant rotates to the process air stream, the pre-conditioned desiccant enables the sorption of water and dehumidifies the crossing process air. Adiabatic re-heat then is released in the air stream and completes the desiccant vapor-compression open cycle. A typical rotating wheel desiccant system releases heat from the regeneration process into the conditioned space when the desiccant wheel rotates from the regeneration stream to the moisture adsorption stream. This inefficiently heats the conditioned space when the overall goal is to cool the conditioned space.
Further, a typical rotating wheel desiccant system is typically designed so that it will operate effectively on a “full load” design day when ambient outside air temperature and humidity levels are relatively high for the geographic area where the system is installed. For example, a typical system may be designed to operate effectively on a “design day” when ambient outside air conditions are at a 0.4% condition for the geographic area (i.e., the load on the system due to ambient outside air conditions would only be higher than the “design day” 0.4% of the time). On any given day when the system is operating, however, the ambient outside air temperature and humidity levels are typically lower than those on the “design day.” Thus, a typical rotating wheel desiccant system is over designed, which causes it to operate in an inefficient manner.
For example, a typical rotating wheel desiccant system has a fixed rotational speed at which the desiccant wheel continuously rotates (e.g., the wheel may rotate 360 degrees in, for example, 3.75 minutes). The rotational speed is set so that the system operates effectively on the “design day” when ambient outside air conditions are relatively extreme. Thus, the speed is set so that on the “design day” the desiccant rotates into the regeneration stream when it has adsorbed moisture to the point that it is no longer effectively reducing the moisture level within the conditioned space. On a typical day when outside ambient air conditions are less extreme than on the “design day,” the desiccant rotates into the regeneration stream when it still has capacity to adsorb moisture from the air within the conditioned space. The regeneration process consumes a relatively high amount of the energy necessary to operate the system, and also inefficiently adds waste heat into the conditioned space when the overall goal is to cool the conditioned space. Thus, it is generally desired to minimize the amount of time during which the desiccant undergoes the regeneration process. With a typical rotating wheel desiccant system, however, the regeneration process continuously operates on a portion of the desiccant and the desiccant enters the regeneration process sooner than necessary.
Typical desiccant systems with a rotary desiccant wheel may also experience increased design, manufacturing, set-up, operating, and/or maintenance costs. Additionally, known desiccant systems may have reduced energy efficiencies while occupying a large footprint for the components. Moreover, conventional desiccant systems may include refrigeration components to dehumidify. Refrigeration components, however, can add complexity, cost, environmental concerns, and energy consumption and operating inefficiencies.